Premature infants' gastric residual volume may be affected by position. This systematic review was conducted to examine the effect of lying position on the gastric residual volume of preterm newborns fed by gastric tube. Electronic databases (PubMed, MEDLINE, MEDLINE Complete, Academic Search Ultimate, CINAHL Complete, Cochrane, and Scopus) were searched for randomized controlled experimental or quasiexperimental studies in English published between 2011 and 2022 investigating the effect of one or more lying positions on gastric residual volume in premature newborns. The PICOS strategy was used in preparing and reporting the systematic review. A total of 304 articles were retrieved, and the full texts of 12 articles were evaluated for suitability. After eliminating the excluded articles, 10 articles were included in the analysis. The quality of evidence varied, with four studies judged to have poor quality whereas the remaining six were considered to range from moderate to good in quality. Based on the results obtained from the studies, it was determined that gastric residual volume was the least in the right lateral and prone positions and more in the left lateral and supine positions compared with the other two positions, with no difference between the two latter positions. The methodological differences, such as the evaluation of different positions, the timing of positioning and the duration of maintaining in the same position, and the measurement times of gastric residual volume made it difficult to reach a definitive proof. We concluded that high-evidence studies evaluating all positions are needed.